Korhonen Marko T, Cristea Alexander, Alén Markku, Häkkinen Keijo, Sipilä Sarianna, Mero Antti, Viitasalo Jukka T, Larsson Lars, Suominen Harri
Dept. of Health Sciences, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland.
J Appl Physiol (1985). 2006 Sep;101(3):906-17. doi: 10.1152/japplphysiol.00299.2006. Epub 2006 May 11.
Biopsy samples were taken from the vastus lateralis of 18- to 84-yr-old male sprinters (n = 91). Fiber-type distribution, cross-sectional area, and myosin heavy chain (MHC) isoform content were identified using ATPase histochemistry and SDS-PAGE. Specific tension and maximum shortening velocity (V(o)) were determined in 144 single skinned fibers from younger (18-33 yr, n = 8) and older (53-77 yr, n = 9) runners. Force-time characteristics of the knee extensors were determined by using isometric contraction. The cross-sectional area of type I fibers was unchanged with age, whereas that of type II fibers was reduced (P < 0.001). With age there was an increased MHC I (P < 0.01) and reduced MHC IIx isoform content (P < 0.05) but no differences in MHC IIa. Specific tension of type I and IIa MHC fibers did not differ between younger and older subjects. V(o) of fibers expressing type I MHC was lower (P < 0.05) in older than in younger subjects, but there was no difference in V(o) of type IIa MHC fibers. An aging-related decline of maximal isometric force (P < 0.001) and normalized rate of force development (P < 0.05) of knee extensors was observed. Normalized rate of force development was positively associated with MHC II (P < 0.05). The sprint-trained athletes experienced the typical aging-related reduction in the size of fast fibers, a shift toward a slower MHC isoform profile, and a lower V(o) of type I MHC fibers, which played a role in the decline in explosive force production. However, the muscle characteristics were preserved at a high level in the oldest runners, underlining the favorable impact of sprint exercise on aging muscle.
从18至84岁男性短跑运动员（n = 91）的股外侧肌采集活检样本。使用ATP酶组织化学和SDS - PAGE鉴定纤维类型分布、横截面积和肌球蛋白重链（MHC）亚型含量。在年龄较小的跑步者（18 - 33岁，n = 8）和年龄较大的跑步者（53 - 77岁，n = 9）的144根单根去表皮纤维中测定比张力和最大缩短速度（Vₒ）。通过等长收缩测定膝关节伸肌的力 - 时间特性。I型纤维的横截面积不随年龄变化，而II型纤维的横截面积减小（P < 0.001）。随着年龄增长，MHC I增加（P < 0.01），MHC IIx亚型含量减少（P < 0.05），但MHC IIa无差异。I型和IIa型MHC纤维的比张力在年轻和老年受试者之间无差异。表达I型MHC的纤维的Vₒ在老年受试者中低于年轻受试者（P < 0.05），但IIa型MHC纤维的Vₒ无差异。观察到膝关节伸肌的最大等长力（P < 0.001）和标准化力发展速率（P < 0.05）随年龄下降。标准化力发展速率与MHC II呈正相关（P < 0.05）。经过短跑训练的运动员经历了与衰老相关的快肌纤维大小典型减少、向较慢MHC亚型特征的转变以及I型MHC纤维较低的Vₒ，这在爆发力产生下降中起了作用。然而，在年龄最大的跑步者中肌肉特征保持在较高水平，强调了短跑运动对衰老肌肉的有利影响。
